The long-term objective of this research is the characterization of regional brain circulation (rBC) in schizophrenic and depressed patients and in controls. The hypothesis being tested is that abnormality in brain circulation may be a correlate of mental illness. If regional circulatory abnormalities exist in schizophrenic patients, we hypothesize that specific symptoms commonly observed in schizophrenia may be associated with localized abnormalities in brain circulation. Further, it is of interest to determine whether there are localized brain circulatory abnormalities in depressed patients. Methods to be used include: 1. A complete psychiatric diagnostic evaluation in order to select 20 schizophrenic patients. 2. A medical history and physical examination for all patients. 3. Brain circulatory adequacy will be evaluated by means of a computerized tomographic (CT) dynamic brain scan of both the supra- and infratentorial regions of the brain following intravenous injection of a bolus of Isopaque, with monitoring via blood pressure (ABP). The importance of this work for clinical studies is as follows: If an abnormality of rBC is found in schizophrenic patients, we will then determine by follow-up of these patients whether the rBC abnormality reflects a state (presence of symptoms) or a trait (dianostic category), e.g., the high RBC to plasma lithium ratio found in patients with bipolar illness is associate with an illness (trait) independently of the presence or absence of symptoms. If an abnormality of rBC is found to reflect a trait, then CT dynamic brain scanning may be useful in characterizing a group of patients, or in defining a sub-population of schizophrenic patients.